Effect of substrate temperature on the properties of pyrolytically deposited nitrogen-doped zinc oxide thin films

The effect of substrate temperature (Ts) on the properties of pyrolytically deposited nitrogen (N) doped zinc oxide (ZnO) thin films was investigated. The Ts was varied from 300 °C to 500 °C, with a step of 50 °C. The positive sign of Hall coefficient confirmed the p-type conductivity in the films deposited at 450 °C and 500 °C. X-ray diffraction studies confirmed the ZnO structure with a dominant peak from (1 0 0) crystal plane, irrespective of the variation in Ts. The presence of N in the ZnO structure was evidenced through X-ray photoelectron spectroscopy (XPS) analysis. The obtained high N concentration reveals that the 450 °C is the optimal Ts. Atomic force microscope (AFM) analysis showed that the surface roughness was increased with the increasing Ts until 400 °C but then decreased. It is found that the transmittance of the deposited films is increased with the increasing Ts. The optical band gap calculated from the absorption edge showed that the films deposited with Ts of 300 °C and 350 °C possess higher values than those deposited at higher Ts.

► Hall-effect measurement introduces the optimum temperature of 450 °C for fabricating p-type high quality ZnO films.
► X-ray photoelectron spectroscopy (XPS) proved the nitrogen presence at the surface of doped ZnO thin films at all substrate temperatures.
► Films prepared at lower substrate temperature (300 °C and 350 °C) own wider band gaps.
► Surface roughness strongly is affected by substrate temperature variations.